Exploring Structure-Sensitive Factors Relevant to Cryogenic Laser Operation in Oxide Crystals Doped with Er³⁺ Ions

Crystals of Gd₃Al_2.5Ga_2.5O₁₂:Er³⁺, (Lu_0.3Gd_0.7)₂SiO₅:Er³⁺ and LiNbO₃:Er³⁺ compounds differing in origin and the nature of their inherent structural disorder were crystalized. Optical absorption and luminescence spectra for transitions between the ⁴I_15/2 and the ⁴I_13/2 multiplets of Er³⁺ ions for the crystal samples were recorded versus temperatures in the region of 80-300 K. Gathered data were analyzed thoroughly providing the in-depth knowledge of the effects of temperature on intensities, wavelengths and bandwidths of Er³⁺ transitions. The information acquired together with the knowledge of significant structural dissimilarities of the host crystals chosen made it possible to propose an interpretation of the impact of a structural disorder in Er³⁺-doped crystals on their spectroscopic properties, and to determine their lasing ability at cryogenic temperatures upon resonant (in-band) optical pumping.